As you may know, WordPress has "Settings" menu tab that contains a submenu with various configuration pages. Wakiro theme extends some of these settings to get more control over the theme features. So, we need to review "Reading" sub page first. You can find "Portfolio settings" item there besides homepage and blog display options. You need to select your portfolio page in the dropdown menu in order to specify parent page for your portfolio posts. Note, only pages that utilize "Portfolio" page temlate are available for selection. You can configure it at any time, when your portfolio gets ready, for example.
Navigate to Settings ▸ Permalinks. Here you can configure common options. Scroll the page down and you will see "Portfolio URLs structure" settings. These are optional and you can left fields blank. But, if you want to change "/portfolios/" in the URL of a single portfolio post, you should modify "Portfolio base" option. Additionally, you can change default "portfolio-category" in the category archive URL and "portfolio-tag" slugs below.